This application claims the benefit of Korean Application No. 2001-68306, filed Nov. 2, 2001, in the Korean Industrial Property Office, the disclosure of which is incorporated herein by reference.
(a) Field of the Invention
The present invention relates to a cathode ray tube and, more particularly, to a cathode ray tube with a shadow mask which is free of deformation while involving improved shock absorption effect.
(b) Description of the Related Art
Generally, as shown in FIG. 11, a cathode ray tube includes a panel 101 with an inner phosphor screen 102, a funnel 103 sealed to the panel 101 while facing the phosphor screen 102, and a neck 105 sealed to the rear of the funnel 103 while mounting an electron gun 107 to emit electron beams 106 therein. A deflection yoke 109 externally surrounds the funnel 103.
A color selection member 121 called the xe2x80x9cshadow maskxe2x80x9d is mounted within the panel 101 such that it faces the phosphor screen 102. The electron beams emitted from the electron gun 107 are deflected by the deflection yoke 109. The electron beams then pass through the shadow mask 121, and land on the phosphor screen 102.
The shadow mask 121 has a rectangular-shaped hole formation portion 121a with a plurality of beam-guide holes, a non-holed portion 121b surrounding the hole formation portion 121a in the shape of a rectangular frame, and a skirt 121c bent from the outer periphery of the non-holed portion 121b to the rear of the panel 101. The respective components of the shadow mask 121 are formed in a body by way of press formation.
The skirt 121c of the shadow mask 121 is inserted into a mask frame 123 to thereby form a mask assembly. The mask assembly is internally suspension-fitted to the panel 101.
When the skirt 121c of the shadow mask 121 is inserted into the mask frame 123 while being sealed thereto, stress is made at the borderline area between the shadow mask 121 and the mask frame 123 due to the outstretching of the skirt. The stress is transmitted to the hole-formation portion 121a of the shadow mask 121 via the skirt 121c and the non-holed portion 121b. 
With the stress, as illustrated in FIG. 12, the relatively weak periphery of the hole-formation portion 121a (the borderline area between the hole-formation portion 121a and the non-hole portion 121b) is sunken, and this results in curvature deformation of the shadow mask 121.
Even though such a curvature deformation of the shadow mask is not visible, it greatly affects the strength of the final product against impact, and hence, it is preferable to reduce the stress transmitted to the hole-formation portion as much as possible.
In order to prevent such a curvature deformation, it has been proposed that a plurality of notches and bead-shaped expansions should be provided in the skirt, or slits should be provided below the non-holed portion, thereby preventing the stress from being generated at the boundary of the mask frame. However, with this method, the effect of preventing the curvature deformation is not so great.
Furthermore, as the outstretching is made at the bottom of the skirt, the length of the skirt may be reduced to decrease the degree of outstretching, thereby preventing the curvature deformation. In this case, the welding point of the mask frame to the mask is heightened so that the flexibility relation between the skirt and the welding point at the possible impact of dropping is deteriorated, and this is disadvantageous in the shock absorption.
Accordingly, it is an object of the present invention to provide a cathode ray tube which enhances the stress prevention effect at the boundary of the mask frame as well as at the welding point thereof to the shadow mask where two or more half etchings differentiated in the etching roughness are made.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
The foregoing and other objects of the present invention may be achieved by providing a cathode ray tube including: a panel with an inner phosphor screen; a funnel sealed to the panel while facing the phosphor screen, the funnel being externally mounted with a deflection yoke; a neck sealed to the rear of the funnel while mounting an electron gun to emit electron beams therein, a shadow mask placed within the panel, the shadow mask having a hole-formation portion with a plurality of beam-guide holes, a non-holed portion externally surrounding the hole formation portion while being shaped with a rectangular frame, and a skirt bent from the outer periphery of the non-holed portion to the rear of the panel, the skirt having a basic etching portion half-etched at a predetermined roughness, the components of the shadow mask being integrated into one body; a welding portion is formed at the bottom of the skirt with a plurality of welding points; and a mask frame internally suspension-fitted to the panel while being welded to the skirt to support the shadow mask, wherein the skirt of the shadow mask has a subsidiary etching portion placed between the welding portion and the basic etching portion while being half-etched at a roughness greater than the roughness of the basic etching portion.
In another aspect of the present invention, the subsidiary etching portion is formed at the central bottom portion of the skirt.
In another aspect of the present invention, the volume reduction rate per unit volume of the subsidiary etching portion by way of the half etching is greater than the volume reduction rate per unit volume of the basic etching portion. The volume reduction rate per unit volume of the subsidiary etching portion by way of the half etching is established to be in the range of 40-60%.
In yet another aspect of the present invention, a plurality of longitudinal slit-typed etching grooves are formed at the subsidiary etching portion while horizontally proceeding parallel to each other. Further, the etching grooves may be partitioned into two or more columns. In this case, it is preferable that the distance Pc between the etching groove columns is established to be in constant proportion to the vertical pitch Pv of the etching grooves.
In yet another aspect of the present invention, the subsidiary etching portion is formed either at the external surface of the skirt, or at the internal surface thereof. In yet another aspect of the present invention, the subsidiary etching portion may be formed both at the external surface of the skirt and at the internal surface thereof. In the latter case, the central axes of the etching grooves correspondingly formed at the internal and the external surfaces of the skirt agree to each other, or are deviated from each other by a predetermined distanced. In yet another aspect of the present invention, a width of each groove on one surface of the mask skirt may be narrower than that of the other surface of the mask skirt.
The foregoing and other objects of the present invention may also be achieved by providing a cathode ray tube including: a panel with an inner phosphor screen; a funnel sealed to the panel while facing the phosphor screen, the funnel being externally mounted with a deflection yoke; a neck sealed to the rear of the funnel while mounting an electron gun to emit electron beams therein; a shadow mask placed within the panel, the shadow mask having a hole-formation portion with a plurality of beam-guide holes, a non-holed portion externally surrounding the hole-formation portion while being shaped with a rectangular frame, and a skirt bent from the outer periphery of the non-holed portion to the rear of the panel, the components of the shadow mask being integrated into one body, and a mask frame internally suspension-fitted to the panel while being welded to the skirt to support the shadow mask, wherein the skirt of the shadow mask is formed using two or more half etchings differentiated in the etching roughness.
In an aspect of the present invention, the skirt of the shadow mask may be formed by way of the half etching such that the etching roughness at the bottom side of the skirt is greater than the etching roughness at the top of the skirt.